If you have a hankering to watch eight minutes of billowing clouds of rocket exhaust, NASA's posted the video of the latest test of its RS-25 engine.
The RS-25 is, as NASA-watchers know, the power-plant the agency is developing to shove its planned Space Launch System skywards.
Yesterday's test was the third time NASA's run …

No. Earth's orbit is safe.

But I hear that one single launch of the SLS will cause runaway global warming that the Earth will never recover from! And the chemtrails from this monster engine ... don't get me started on the chemtrails!

Re: 8 million pounds thrust

Whilst I dont have a good way of describing the thrust in el reg units I do know a good video showing the mass of fuel burned per second in elephants for the saturn 5 which is in the same ballpark as the SLS

Blue whales.

According to Martin Burkey, of NASA’s Space Launch System team, RS-25 produces 512,000 pounds of thrust, that’s more than 12 million horsepower and "makes a modern jet engine look like a wind-up toy".

Unfortunately this also makes NASA look like a wind-up, because horsepower is, well, power, and power is distance moved per unit time (kinda like speed) multiplied by force (er, thrust) so it's back to school for Mr. Burkey and well done elReg for not falling into the bear trap.

Re: Blue whales.

Re: Blue whales.

Surely the problem with a 12 million horsepower rocket, is that all the horses will gradually catch fire. Is that why rockets keep dropping stages as they rise?

This must be the great SpaceX innovation. He's not landing his rockets in order to re-use them. He's bringing them back because of delicious horsey barbeque. Or should that be braai? I guess you can take the man out of South Africa...

Re: Blue whales.

Quote: distance per unit time is velocity and has nothing to do with either thrust or power

You have misunderstood what the OP wrote. What he actually said is: "power is distance moved per unit time multiplied by force" (which is correct). There was a parenthetical remark after "time", but it didn't end the definition of power.

Re: Blue whales.

Unfortunately this also makes NASA look like a wind-up, because horsepower is, well, power, and power is distance moved per unit time

And therefore the power in the exhaust is calculable: you're moving known mass at known velocities. In public discussions, this often leads to incredible numbers about how many horsepower some rocket engine develops. In engineering discussions about nuclear and electric rocket analyses, the jet power becomes somewhat important because the available input power (from the reactor, solar panels, or hamsters in wheels) imposes limits on the possible output power, and therefore maximum possible thrust and exhaust velocity.

If my memory hasn't completely failed me, I recall the equation being like:

Power = 0.5 x [exhaust velocity] x [thrust force] / efficiency

An ion engine with a specific impulse of 3000 (exhaust velocity of ~30,000m/s) that develops 1 pound of thrust (4.5 Newtons) via a mechanism 50% efficient (typical for electric rockets) requires an electrical input power of:

0.5 x [30,000m/s] x [4.5N] / 0.5 = 135,000 Watts

While its exhaust has 62,500 Watts and the engine's radiators are handling a similar 62,500 Watts.

In the late 1950s, the US sketched out a number of nuclear-thermal rocket designs rated by their gigawatts of output, like the 12-gigawatt and 14-gigawatt rockets considered for the Helios and Hyperion rockets. The uranium in the engines could only produce some much power to warm and expand the exhaust, and it was critical to understand what that value was.

"Won't 8 million pounds of thrust also knock Earth out of it's current orbit and crash us into the moon?"

Don't be silly, of course not. They always fire the exact same engine twice, 12 hours apart, so that the effect gets pretty much cancelled. They have strict regulations for that kind of thing you know!

"Won't 8 million pounds of thrust also knock Earth out of it's current orbit and crash us into the moon?"

There will be a minuscule effect on the Earth, every force having an equal and opposite reaction and all that stuff but the Earth is very big and very very heavy when compared to a rocket so I really wouldn't worry about it.

Anyway the Moon is receding so any change to the Earth's orbit won't be enough to catch the Moon. also as the Moon orbits the Earth if the Earth's orbit was disturbed the Moon would just tag along for the ride staying in much the same orbit as now.

12 hours apart

This, of course, causes the earth to become slightly less oblate, which is why you satnav/gps occasionally demands you adopt a stupid route through a mamor metropolis during rush hour instead of going round the bloody thing.

Lawn-laying instructions?

Re: Lawn-laying instructions?

My favourite part of the xkcd Up-goer 5 Illustration is the arrow to the rocket nozzles which says "If this starts pointing towards space, you are having a bad problem, and you will not go to space today."

Gives you perspective...

SpaceX Launches and Landings seem so routine and feel like they only last a few moments, but this gives you perspective on how long a SpaceX/Nasa Launch seems to a an avidly watching, apprehensive Rocket Engineer.

Re: Rocket powered car

Re: Rocket powered car

Yes. Because nobody will be able to catch you. Or probably find your body after the inevitable crash and burn boom.

However you will need to modify your car slightly - as you'll need a slightly larger fuel tank. And your fuel bils may increase just a teensy bit. 10,000 mile services will also become a tad more expensive, but seeing as you're unlikely to live that long - this shouldn't be a problem.

Re: Rocket powered car

Re: Rocket powered car

Will I be able to use one of these to power my car after petrol & diesels are banned [in the UK] after 2040?

The RS-25 is fueled with hydrogen and oxygen, which produces copious amounts of dihydrogen monoxide. Besides being known for eroding mountains and being bound in most tumors, dihydrogen monoxide is a potent greenhouse gas. Given the way REACH and the UK's Environment Agency have been going, they'd probably try to ban it and anyone who tried to correct their grasp of chemical nomenclature.

Re: Rocket powered

Re: Rocket powered

I like your thinking, a steam powered car would be a more sensible option for transport after 2040. True Stephenson's original was a bit slow, but this bad boy, "The fastest kettle in the world", can do over 140 mph*.

(*Needs a bit of a run up to get to that speed, preferably a nice flat 2 mile runway. Also emits copious qualities of DHMO)

Re: Rocket powered car

@Swisss Anton -- Re: Rocket powered car

Will I be able to use one of these to power my car after petrol & diesels are banned [in the UK] after 2040?

I recall a video (I think it's been discredited) of a lad who put a JATO bottle in the trunk (the thingy in the rear) and ignited it. It became airborne and killed him and ended up in a zillion pieces. So.. the answer is.. don't try it.

Re: Rocket powered car

Due to timing the controller uses 2 MC68k processors on the same chip.

Which were only mfg for NASA for this task.

So probably run out of chips.

The RS25 was one of the jewels of the Shuttle programme. There were a fair few mods that could have made it both higher T/W and more reliable. Using it in expendable mode is deeply stupid. Hopefully this time round they will use actual off the shelf chips.

Since it will operate no further than LEO they don't really need to be space rated either.

Re: Due to timing the controller uses 2 MC68k processors on the same chip.

One model of Raspberry Pi got "space rated" (specifically for use on the ISS). I don't recall, off hand, which model, but it was either the B+ or the Pi2B. The former, I think, as it wasn't the current model when launched and the Pi3B hadn't come out yet.

everyone can stick to their rubbish rockets, imposible drives, and ion drives

multiply BAE System railgun spec's by 1000, and you will have 100 tons shooting off with zero acceleration at 256 million MPH if your up in space, from a single pulse of compressed retracting magnets as you do not need a rail

2 fixed magnets inside of a tube acting as a thruster, one of the fixed magnet's will be what pushes your craft along and creates thrust if you get the timings, distance and force/gauss correct

after you have spent a billion or so rewriting all the math for thrust, and able to calculate all the velocities in space with all the physics and terminal velocities, and know the forces it takes to turn and accelerate within a given gravity, you have zero acceleration, just like an electric car has maximum torque all the time

if you have government backing, the most you need is a 0.5MW nuclear reactor for a 900 ton shuttle full of 3d star map navigation, topologal radar navigation system and a full science lab with catscans etc in, if you not carrying a satellite etc

you could easily generate 500,000KW from normal fuel, you just would'nt be able to go beyond the moon

if a nuclear submarine in todays world cost £1bn, a new shuttle would be around £3.5bn, so for the cost of building another useless international space station, you could have 30 or more shuttles flying around the whole solar system doing real science, and destroying NEO's and fighting aliens with railguns and MoD's dragon fire microwave laser cannons

so you can have nano tube force fields in toughened graphite hull you can fix with polymer from a tube, for small space debris not picked up on the topological radar system that is generating real time debris in the 3d star map navigation system

a easy engine would be frontier elite dangerous, its all "1:1", if you put your vector math in from control gyroscopes, and able to keep adding your scanned planets into the database until you need DNA data storage

submarine radars can easily pick up a gold fish 100 miles aways,

the design would also need to be curved for solar storms to pass by smoothly, flying along in a brick will kill you through radiation and debris having nowhere to go, and then fold down the rear fins when in space

Re: "I'll put my money on a Skylon."

why a cleaning job get the thumbs down, its a easy £600 a month tax free if you live in the area or a comment moderator, your never allowed to touch nothing in machine shops or main offices except the floor

you can move on to cleaning aeroplanes at your local airport at night £15ph, then power stations for £25ph

Re: "I'll put my money on a Skylon."

Re: "I'll put my money on a Skylon."

im perfectly fine, depending on the compound, toughened graphite can be upto 10x stronger then the carbon which holds a forumal 1 cockpit together during a 36G head on crash

if you have toughened graphite, which would probably be a classified compound on a shuttle, then aerogel, and then carbon, you will have a light weight super strong hull which would survive space which the US air force x-37b hull is probably made of. then if you spray with a silicon spray, your hull will then be tough like a diamond, and is generally the ultimate glue on a building site, so you will have to bring out blow tourches and drills to break through the stuff, which is also used to hold roofs together during a storm

if elite dangerous engine is 1:1 scale, it should be easy enough to make a scale model of you craft, and add your EM drive power and gyroscope vectors into it, so you know your position in the solar system beyond mars because the sun will just be a dot and you will easily be lost without a 3d star map

making a true 1:1 star map is all part of the real science you can do while having a shuttle that has some speed, and if a next gen shuttle was 900 tons, that would make it roughly 4.5x bigger then NASA old shuttle, and with no fuel in the wings, comes more food for the outter reaches

Re: "I'll put my money on a Skylon."

if you shoot off at 256 million MPH, it would take 16 hours to reach the edge of the solar system going half the speed of light, but even a months journey would still be better then the 30 years it took voyager to get there

if you went faster then 256 million MPH, you would outrun your radar navigation system and would'nt have any space debris being mapped

Re: "I'll put my money on a Skylon."

electro magnets can go upto 1MW, compressing those would give you more gauss then the gravity of a neutron star, there is no gravity in space that could make a simple retracting magnet truster become useless, cancelling out your thrusters magnetic fields

to hover, you just have to carry on with the jump jet hover and landing, which would also apply to re-entry of atmosphere's

Re: "I'll put my money on a Skylon."

if you have toughened graphite, which would probably be a classified compound on a shuttle, then aerogel, and then carbon, you will have a light weight super strong hull which would survive

.

Though I've worked with a range of graphite composites (carbon-carbon to carbon-reinforced bismaleimide) in my career, I'm not quite sure what you're getting at. "Toughened graphite" isn't a standard material product, and any "toughening" of graphite is relative - graphite is always a soft, brittle material, even when its tensile strength heads for 1 million psi / 6,900 megapascals. I used to chop and prepare ultra-high strength, woven graphite sheets with common steel scissors. I never had to sharpen the scissors once, there was no wear of the steel from such brittle, soft materials. (I did learn to wear a filter mask after I began coughing and sneezing black snot while chopping the graphite, but that's a different matter.)

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space which the US air force x-37b hull is probably made of.

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The X-37B's outer skin uses conventional, shuttle-type heat shielding. The nose cap is a carbon-carbon composite with silicon carbide oxidation barriers, like the shuttle's leading edge. The belly is lightweight, fiber-reinforced silicaceous material, a modest improvement on the shuttle's tiles. The underlying frame is mostly polymer composite (where it's not aluminum) like high temperature bismaleimide-carbon composites. (I'm not sure of the exact choice of resin, but BMI functions up to 250C, better than conventional aerospace aluminum alloys, and is a good example for this discussion until I can confirm it.) So, the X-37B's framework is in the family of composites with the 787 and F-35 aircraft, not "toughened graphite and aerogel."

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Given the X-37B's relatively restricted budget, you're not going to see a lot of exotic material choices - truly new material systems really take upward of 10 to 20 years to go from the lab to operational hardware.

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then if you spray with a silicon spray, your hull will then be tough like a diamond,

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1) Diamonds are not very tough; their KIC (K-one-cee, I need to learn HTML subscript codes) fracture toughness is low compared to metals and polymers. They are hard and can be quite strong, but "toughness" is not something usually associated with diamonds.

2) Spraying silicon onto carbon usually results in either carbon with silicon on it or - if you pick an exotic process like plasma-assisted chemical vapor deposition - you can get a thin layer of silicon carbide below the excess silicon. It's usually better to deposit your final material (you seem to like silicon carbide) directly on the substrate rather than hoping for less-controlled reactions between raw elements.

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The chemical vapor deposition industry has some precursor gases that will decompose and reliably produce silicon carbide on graphite. I used to do that when making carbon-carbon composites to track the speed of graphite deposition. To figure out graphite deposition speeds, we'd interrupt hydrocarbon flow through the reactor and flow...it was a pyrophoric methyl silane compound with some chlorine, but I don't remember the exact name, just the fireballs when it leaked into air...anyway, a silane compound that would break down and deposit silicon carbide. You'd have visually distinct SiC layers between graphite can could figure out the millimeters-per-hour of graphite growth. Or you could make graphite-reinforced silicon carbide and skip the graphite deposition, though that wasn't my employer's goal.

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Speaking of reinforced silicon carbide, you might want to ask if carbon and aerogels are the way you really want to go. There are some fantastic high temperature materials out there, like the tantalum and hafnium carbides, and fiber-reinforced silicon carbides have been in limited production for decades.

Re: "I'll put my money on a Skylon."

i doubt the x-37b is made from alloy, for the size of it, the rest would have to be 50% copper to last 3 years in space and being smashed by all the debris

you have NASA working on carbon plane frames along with spaceX, the main reason why you would have toughened graphite is the ease of being able to fix it with a quick space walk with polymer from a tube as the fibres have no specific order, which would also help if a nano tube force world would be used

if a shuttle was able to hover, with a jump jet system, then you can use the same system for entering atmosphere's and would'nt need ceramic heat sheids to handle the 6000c plasma build up

then you will need something that can easily be fixed if you are travelling at X MPH after compressing magnets, even the best radar won't pick up dust and you also would'nt be able to navigate around dust

Re: "I'll put my money on a Skylon."

The main reason you wouldn't is that "toughened graphite" doesn't exist.

is the ease of being able to fix it with a quick space walk with polymer from a tube as the fibres have no specific order

Aerospace grade resin systems typically require hours, if not days, in controlled environments for final cure to their specified strength. You don't squeeze a tube of goop and get a quick super-strong bond. You'd only do that for a cosmetic fix, like a scratch in a gel coat, or some non-strength critical application like encapsulating an electrical connector.

Real composite repairs tend to take three forms where I'm employed:

1) A little dab of adhesive on a carefully cleaned, scuffed, and primed cosmetic scratch

2) A large, carefully applied, overlapping patch of fibers and resin, to be followed by a 7-day cure (or 2-4 hours if the part can go in an oven)

3) No repair, scrap it. Most of our engineering for parts with damage to their fibers is to toss the part rather than repair it. But this is a production environment where we're building stuff, not a situation with fielded hardware.

i doubt the x-37b is made from alloy

Why? The running joke at my aerospace employer (in my materials engineering group, anyway) is, "Sure, you can make your part out of any material you want so long as it's 6061-T6," (a common aluminum alloy and temper.) The data requirements for introducing new materials into flight hardware are ludicrous, designers won't touch new materials until they have well-developed A- and B-basis values for the major properties. Aluminum alloys like 6061 and 7050 have well-known properties and are strong enough, tough enough, and cheap enough for the job.

Aluminum alloys are a workhorse in space. The International Space Station's modules have aluminum pressure vessels (mostly 6000- and 7000-series alloys) and even aluminum Whipple armor panels. The shuttle used aluminum for its frame - a major design driver in its heat shielding was to keep interior temperatures low enough that aluminum was acceptable for the wing spars.

I know The X-37B uses composites. The USAF and NASA brag about "expanded use of composites" in the X-37. But, given most of the work is done by Boeing and Lockheed Martin Skunkworks, you can take a guess that they're working with carbon fiber-epoxies like the 787 or carbon fiber-BMI like the F-35. And because those are the players, they'll be also be using predictable aluminum alloys in less critical areas, too.

Re: "I'll put my money on a Skylon."

alloy is a joke in space, its reinforced with 8 inches of copper on satellites so space dust cannot penetrate vital parts, and belongs in the 1990's, and would also be alot more weight having to carry extra alloy plating if abit of space debris between the size of dust and a minoe/goldfish, hits your hull with a terminal velocity of probably 200,000 MPH +. as man's first deep space shuttle would'nt just be shooting off at half the speed of light

having some modern classified toughened graphite compound would make alot easier when it comes to fixing a hull, as the hull would'nt be less then 1 inch thick

even if you beat a toughend graphite tennis racket with a hammer, it will end up in alot better shape then a alloy racket

Re: "I'll put my money on a Skylon."

bottom line anyway, in todays world there are enough carbons, graphites and silicons, to which you should be able to make new hull material including some form of collision phsyic's if you are going to carry on using 6 -> 8 inches worth in depth

Re: "I'll put my money on a Skylon."

Out of curiosity (and I know I'm going to regret asking), where and how in the seven shades of hell did you come up with "8 inches of copper"? Do you have any idea what one square foot of copper, eight inches thick, would weigh? That's just about 373 pounds, or near enough 170 kilos. Can you point me at anyone lifting this kind of mass out of Earth's gravity well just for shielding?

Re: "I'll put my money on a Skylon."

its in TV programs that have been on since the 1990's, 5 copper plates 1/4 inch thick, 1 -> 2 inches apart, and that is used to stop space dust

The International Space Station's Whipple panels use sheets of 6061-T6 aluminum, usually with Nextel ceramic fiber sheets or Kevlar polymer fiber sheets in between the aluminum. I recommend reading the link - it's a detailed look at different models of the orbital debris threats that NASA used, the analysis techniques to develop armor including some coverage of the hydrocodes, and a discussion of the different forms of shielding on the station depending on location and anticipated threats.

Re: "I'll put my money on a Skylon."

and there are plenty of photo's which show's those panels do not work, NASA is useless and too poor and has falling a long way behind the rest of the world of doing any good, they have to spend most of their money on the useless SLS

the ISS sheilding would be 100% useless on a shuttle which shoots off at a minimum speed of 200,000 MPH so you could get to mars in a few months or a day

material using some kind of collision physic's will be like http://www.esa.int/spaceinimages/Images/2013/04/Hypervelocity_Impact

all of NASA's sheilding for every meter/sq would way around 8KG, while graphite/silicon based hull would be around 1KG

Re: RS-25 turbo pump

There are actually 4 turbo-pumps, 2 low pressure and 2 high pressure for fuel and oxidiser. And they're surprisingly low pressure, fuel goes up to 45 bar, oxidiser only up to 30 bar.

I didn't easily find the answer in a few brief Googles. I think I found total propellant flow at 100% throttle, which is 1409 kg/sec. Which is both oxygen and hydrogen.

Which is quite impressive - given the turbo-pumps only weigh something like 50kg.

To put this into context, the UK rivers authority own 2 extra-large pumps for flood clean up. Each does 500 kg/sec - at much lower pressures too - and each completely fills the loadbed of a large articulated lorry.

The pumpset for Wembley stadium does 60 kg/sec and is 16m long by 800mm wide by 1m high. I happen to know that, because we lost that contract...

Oh, and the oxidiser high pressure turbo-pump is a mere 26,000 horsepower!

What you've missed is that each of those pairs of turbo pumps operates in series.

What you've listed is the output pressure from the Low Pressure Fuel & Oxdizer TP's.

The "High Pressure" TP's are driven by the flow from the Preburner and are more like 7000psi (around 470bar) (to feed the Preburner) feeding the Main Combustion Chamber operating with a back pressure around 2-3000psi.

Given that studies of engine costs suggest that development costs scale as the cube of maximum chamber pressure this may explain why SSME was such an expensive engine (it's also pretty big and uses liquid Hydrogen, neither of which help).

Re: RS-25 turbo pump

"To put this into context, the UK rivers authority own 2 extra-large pumps for flood clean up. Each does 500 kg/sec - at much lower pressures too - and each completely fills the loadbed of a large articulated lorry."

To be fair, those include the generator, motor, fuel tanks and filters too. And they are built to last more than a few minutes of use.

Heavy Rocketry

Re: Heavy Rocketry

The Russians do very well with the Soyuz. It's an old basic design and not terribly efficient, but it's been exceptionally reliable. NASA tends to design for maximum efficiency and reliability be damned.

Back of a fag packet

If we were being green we'd replace all this nasty noisy stuff with helium balloons.

If we need 8E6lbs of thrust that's 3.5E9g. Now a 2l party balloon filled with helium will support about 2g so all we need are 1.75E9 helium balloons ... or, in honour of the great film, 1.75 Ups per launch and a big balloon pump ...

Re: Back of a fag packet

The problem with the He balloon proposal is that all He on Earth is a byproduct of radioactive decay (Alpha particles). This would mean that your balloon system would be nuclear powered and there would be more untutored, tofu-eating, sandal-wearing, wet liberal protesters painting their faces and laying down on railroad tracks than could be secretly sponsored by the minority political party.

There is also a big problem with He availability for any vigorous launch campaign.